Method for using direct blast-furnace metal for foundry castings



Patented Apr. 21, 1925.

UNITED STATES PATENT OFFICE.

avin r. BAKER, or vTamar'rowxr, NEW YORK.

' No Drawing.

To all whom it may concern: Be it known that I, DAVID F. BAKER, a citizen of the United States, residing. at Tarrytown, in the county of Westchester, State of New York, have invented a new and useful Method for Using Direct Blast- Furnace Metal for Foundry Castings, of which the following is a specification. I

My invention 'relates to improvements' in method for using direct blast furnace metal for foundry castings. The object is to provide an improved method for making iron, in a coke blast furnace with such silicon and sulphur content, as shall be suitable, in the liquid state as it comes from the furnace, for foundry castings, having the necessary strengthand other required physical qualities.

Heretofore hquid iron, as it comes'from the blast furnaces, and which I shall call direct metal, has not been successfully used for producing castings having small sections, which usually require a fairly close grain, and especially a strong iron.

Heretofore the blast furnace has-made iron of varying grades, cast into pigs for the foundry. The foundries have melted it in small furnaces, as a rule cupolas, using such mixture of the difl'erent grades ofpig iron, with possibly the addition of scrap,"as experience has taught them will give the necessary physical characteristics in their castings. The practice is to use the cupola merely to remelt and not to purify the metal, i. e. if any limestone is used, it is used merely. to flux the ash of the coke and any "small uantity of dirt which may come in with t e charge, and the slag is made at; the

the ast amount of coke will be required for melting it.

The blast furnace, of necessit carries a from .60 per cent to 1.00

cheapest point, namely, very fusible, so that Application filed February 29, 1924. Serial 1T0. 698,087. g

The average coke used in cupolas runs per cent 1n sulphur, and if this sulphur is figured as. going into the iron, it will be seen that there will be a material increase of sulphur in the melt.

Taking an open grained iron, with a given silicon content, and adding sulphur in increasing quantities will give iron with increasing fineness of grain and increasing chill, due to increasing the combined carbon, until the iron becomes so hard as to be too brittle to be used for castings. The increasing sulphur also causes blow holes in increasing quantity and size, until the iron is worthless for castings.

Now as the conditions of remelting necessitate an increase of sulphur, and asthe foundryman does everything he can to keep the sulphur as low as'possible by using raw materials as low in sulphur as economical operation will allow, the result is a fairly constant sulphur content, but above .04 per cent, as a rule. The foundryman has found by experience that, if he wishes to open the grain of a' casting, he must increase the silicon, and if he goes below a certain point with the silicon, the iron will be too close grained to use; consequently he has been limited to the use of comparatively high silicon irons.

The blast furnace man, because he has been compelled to make many different grades of iron to meet the demands, of various processes, in addition to the foundry requirements, has learned to control the elements in pig iron within very close limits, especially the siliconvand sulphur.

From long experience in making the different grades of pig iron in the blast furnace and observation oftli'e iron of each, I have discovered that, ,-for instance, an iron may be made in the-blast furnace,with, for example, 1.00 per cent silicon, which will have similar characteristics to iron of, for example 3.00 per cent silicon, from a on 01a, providing the sulphur content of the last furnace iron is made low enough; also, that by holding the silicon at, for example, 1.00 per cent, and varyin the sulphur, changes in the physical quahties may be produced similar to the changes obtained b varying.

the silicon in cupola metal, the su phur actmg in the opposite way from the silicon;

i. e. a drop in sulphur acting as an increase in silicon, but with a much stronger effect.

In accordance with my method, in the case ofcastings requiring strength, the procedure would preferably be to burden the furnace for an iron having an ordinary or normal basic iron silicon content, say 1.00 per cent, and to control the sulphur content, by methods well known to blast furnace men, to a point which-would be lower than would depend somewhat on the percentage of other elements present, such as phosphorus, titanium and manganese. Under other conditions it will be preferable to operate a furnace, as above described, except that economic considerations will require a range of silicon content from 1.25 per cent to 1.50 per cent.

By my methods it is possible to make open grained castings of' fairly large sections, from direct metal of materially lower silicon content than has heretofore been produced, and also to make equally satisfactory castings for other purposes from direct metal, with any range of silicon practical to make in a blast furnace, by giving it the proper sulphur content.

The following advantages or economies are claimed for the improved method herein described;

(a) Saving the cost of remelting cold pig iron, by using the liquid iron direct, as it comes from the blast furnace.

(b) By using a lower silicon iron, the difference in the cost between producing low silicon iron and high silicon iron, in a blast furnace, is saved, since it is well known that for the manufacture of the higher silicon iron, more heat is required to reduce the additional silicon, and consequently more coke is required and a lower tonnage of metal per dayis obtained.

The method herein described may be used advantageously in the manufacture of what is known in the art as the de Lavaud pipe.

As the control of the blast furnace, is well known in the art, I do not deem it necessary to give any particular descriptign of the same.

What I claim is a 1. In the art of direct metal'casting, the

- method which consists in varying the combined carbon in pig iron by varying the $111 phur content, and maintaining the remaining elements at approximately the same percentage.

2. In the art ofdirect metal casting, the method which consists in changing the percentage of combined carbon in castings made from low silicon iron, by varying the percentage of sulphur in the iron.

8. The method of controlling the combined carbon in castingsmade from metal taken direct from the coke blast furnace, which consists in holding the silicon at about 1.00 per cent and varying the sulphur content as required.

4. The method of producing direct metal castings, which consists, while preparing the metal in a coke blast furnace, in keeping the silicon low and maintaining a proper ratio between the sulphur and silicon content, with the other elements remaining approxi mately the same, so that the castings made from direct metal will show a gray fracture.

5. The method of preparing liquid pig iron, to be used direct from a coke blast furnace for the manufacture of cast iron pipes, which consists in producing the usual basic pig iron and so burdening the furnace as to produce a sulphur content lower than the usual basic iron analysis, and in required proportion to the silicon content.

6. The method of producing castings ofnormal strength, from metal taken direct from the coke blast furnace. which comprises lowering the silicon and sulphur content to a point required to.secure suitable fluidity of the metal.

' 7. The method of making castings of normal strength which consists in using pig iron direct from the coke blast furnace, containing less than 1.50 per cent silicon content, and in which the sulphur content is controlled so as to secure satisfactory relation between the combined and graphitic carbon in the finished casting.

8. The method of making castings of normal strength by using metal taken direct from the blast furnace, which comprises reducing the amount of coke normally used in the furnace, inorde'r to produce a low silicon iron, and at the same time fixing the quantity and analysis of the slag to produce a sulphur content sufliciently low to maintain the fluidity of the liquid pig iron.

9. The method of making castings of normal strength from direct metal as it comes from a coke blast furnace, which consists in burdening the furnace for an iron having a silicon content between 1.25 per cent and 1.50 per cent, and controlling the sulphur content to a point substantially below normal practice.

10. The method of making castings of normal strength from direct metal, as it comes from the coke blast furnace, which consists in burdening the furnace for an iron having a normal basic iron silicon, and controlling the sulphur content to a point substantially below normal practice;

11. The method of makingcastings of normal strength from direct metal, as it comes from the coke blast furnace, which consists in burdening the furnace for an iron having a normal basic iron silicon, holding the sulphur content at at below normal point, and varyingthe silicon content as required but still keeping it very materially below that in normal practice.

DAVID F. BAKER. 

